(1) Field of the Invention
This invention relates to scanners, in particular to multiple reflection optical system of the scanners.
(2) Brief Description of Related Art
An optical system of prior art is shown in FIG. 1. The scanner has a scan window 10, over which a document 12 to be scanned is placed. A light source L scans the document 12 and a light ray containing the image information of the document is reflected. In the multiple reflected path optical system, the reflected light ray undergoes multiple reflections in sequence: reflected by a mirror 161 at point A, reflected by a mirror 162 at point C, reflected by a mirror 165, reflected by a mirror 164, reflected again by the mirror 161 at point B, reflected again by the mirror 162 at point D, reflected finally by the mirror 165 before reaching the image sensor 18 through the focusing lens 14. In this optical system, the focusing lens 14 is enclosed by all the reflecting mirrors. The reflecting mirrors 161 and 162 must be separated vertically from the reflecting mirrors 163 and 164 by a certain distance to allow the placement of the focusing lens 14. This vertical distance determines the vertical dimension of the scanner frame.
An object of this invention is to reduce the vertical dimension of a scanner. Another object is to reduce the cost of a scanner.
These objects are achieved by placing the focusing lens outside the area surrounded by the reflecting mirrors, so that no vertical space between the reflecting mirrors need be allowed for the focusing lens.